Critical limb ischemia (CLI), a lack of blood flow to the leg characterized by leg pain at rest or by tissue loss, affects approximately 2 million Americans and is characterized by increased rates of cardiovascular and limb complications. Management of CLI is rapidly evolving, with the advent of minimally invasive techniques to restore blood flow and advances in wound care. However, there is little consensus regarding optimal treatment. The ongoing NIH funded BEST-CLI is designed to assess the comparative effectiveness of minimally invasive versus full surgical restoration of blood flow in CLI, however, little is known about current nationwide practice patterns, outcomes, quality of life, and healthcare resource utilization in CLI. Additionally, the BEST-CLI trial will enroll a selected patient population that may not be fully representative of ?real world? CLI patients. As a result, in conjunction with the BEST-CLI investigators and BEST-CLI Trial, we propose the companion BEST-VIVA registry (vCLI) to investigate the following aims: 1) Describe the baseline demographics, comorbidities, and treatment strategies of consecutive patients excluded from the BEST-CLI Trial and included in the vCLI registry, with a focus on variations in care 2) Describe the clinical outcomes ? specifically major adverse limb events (MALE) free survival, wound healing, and major adverse cardiovascular events (MACE) - by treatment strategy in CLI patients, with a focus on causes of outcome variation within treatment strategy 3) Describe healthcare related quality of life and healthcare costs, by treatment strategy in the vCLI registry, with a focus on causes of variation in quality of life and costs. Methods: The vCLI registry will be funded by a unique public / private partnership with governance from both vCLI primary investigators and BEST-CLI primary investigators. For Aim 1, Multilevel multivariate regression will be used to identify patient, physician/hospital, and geographic factors associated with variations in treatment strategies. For Aim 2, Kaplan Meier and cumulative incidence estimates of limb and cardiovascular outcomes will be stratified by treatment strategy and other subgroups of interest. The impact of diabetes and CKD will be quantified by multivariable modeling and clinical risk prediction scores will be developed separately for each treatment strategy. For Aim 3, quality of life, costs, and cost effectiveness will be described for each treatment strategy and sources of variation within each treatment strategy will be identified via multivariable regression. Impact: The results of the grant will help to illuminate current practices and outcomes in the care of CLI. Data generated regarding patient demographics, variations in clinical outcomes, and variations in costs / cost effectiveness will serve to 1) identify targets for future healthcare systems interventions to improve adherence to guideline recommended care and 2) provide context and generalizability for the findings of the BEST-CLI Trial and 3) identify specific healthcare systems targets to help speed the adoption of BEST-CLI trial findings into clinical practice.